Ok, enough with the plastic water pump impelers

[bmw540san]

Originally Posted by williamx5

I agree totally!! The two recent water pump failures I had were not a result of the impellers... Just the outer bearings coming apart... The impellers actually stayed together...

Additionally, the local parts store version I did purchase failed less than 30 minutes of run time... It's impellers did come apart when the bearing failed...

Cheers!!!

Good point.
I remember some time ago needing a WP the same day and going to Pep Boys.
I don't care much for them but they did have Bosch WP in stock for E39 I6 IIRC. I took it out of the box and it had big heavy cast impelers and the casting looked very rough.
On the other hand I just replaced original WP on my X5 (14 y / 109 k)
It was weeping and the bearing was starting to go but composite impellers looked good and I've actually tried to break and bend them with no success.
I used Italian made OEM Saleri with composite impellers stamped INA Germany. The gasket seemed inferior and it did leak upon installation until I went with Victor Reinz gasket with black silicone bead embedded on one WP side of gasket.

[StephenVA]

Welcome to world sourcing of auto parts and their components. Some vendors just allow their buyers to select who can build the cheapest and meet the min standards. Others build everything in house to control warranty, defect rates, and then costs. Low volume vendors always go for cheapest components/parts as that is their way into the market..."We are the cheapest!"
The great rule of DIY to follow is always use OE or the OE/OEM replacement parts, if you are planning to fix it once for life. Then again, its your efforts, time, and $$ so you get to choose the path that fits your life. In the repair world this second path is called the "Coat Hanger Method"

For the "but there are exceptions"...crowd, there are always improved parts from some vendors that are designed to resolve OE manufacturing short comings. Example Meyle HD thrust arm bushings to name one.
This forum and others do a great job pointing out what to watch for in buying parts. Thanks for bringing up Water Pump impeller misinformation/noise.

I have a welded impeller WP running in a E39 for now going on 8 years with no issues. I pulled it out last year for an inspection while doing other repairs and just put a new seal on it as I touched it.